Temperature-responsive bimetal tripping device



'r. s. BASSE 3,470,516

TEMPERATURE-RESPONSIVE BIMETAL TRIPPING DEVICE Sept. 30, 1969 Filed April 28, 1967 FIG. 3

FIG. 2

United States Patent Int. (:1. noih 37/52 U.S. (ll. 337-335 3 Claims ABSTRAT OF THE DISCLOSURE I A device usable principally in electrical circuit tripping in response to temperature variations representative of variations of some variable operating condition of the circuit or phenomenon including a trip actuated by a pivoted operator actuated by a bimetallic element responding to the temperature variations. The movement of the operator is compensated for temperature variations not representative of a change in operating conditions by a compensating bimetallic element variably defining automatically in part different pivot points for the operator. The variable positions of the pivot will thereby define the different tripping points or values of the operating conditions at which tripping takes place. The range of variable positions of the pivot is set manually.

The present invention relates to temperature-responsive bimetal tripping devices for us in electrical circuits and more particularly for a compensated bimetal tripping device in which the trip point is preset manually and is automatically and tripping is thereafter effected.

Temperature-responsive tripping devices are known which respond to overload and in which one or more bimetallic strips, heated by the electrical current, act on a slide or operator which is displaced in a direction parallel to itself. The slide operator acts upon a rocker arm or operator which will trip the device and Whose free end actually actuates the trip device while its pivot point is influenced by a compensation bimetallic strip.

Generally, the compensation bimetallic strip moves in the working plane of the rocker arm under the influence of temperature and thus, eliminates the effect of ambient temperature on the point at which tripping takes place. The compensation bimetallic strip is displaceable in its own working plane so that the trip point can be set. Usually, the compensation bimetallic element is designed as a two-armed rocker which bears on a displaceable eccentric plate with its free end.

This type of construction has the disadvantage that the displacement mechanism, i.e., the eccentric plate with a handle thereon and the associated scale, for setting the trip point, occupies a very large space which is either square or circular whereby the width of the temperatureresponsive tripping device is increased, in comparison with the other components thereof, to a very great degree. Moreover, in the known devices the length of the compensation bimetallic element generally corresponds to the length of the working or operating bimetallic strip or element so that the height and/ or length of the temperatureresponsive tripping device is increased in comparison with the dimensions determined by the working bimetallic strips, the trip element and the trip switch.

A principal object of the present invention is to provide a temperature-responsive bimetal tripping device which is made very small and compact.

A feature of the tripping device in accordance with the invention is that a compensation bimetallic element is displaceable in a plane substantially perpendicular to the working plane of the trip element and the trip element or an element coupled therewith, has an inclined surface at a point of contact or cooperation with a compensating bimetallic strip. This surface is inclined relative to the working plane and a plane of angular displacement of the compensation bimetal element. Even though the maximum displacement of the compensation bimetallic strip is limited by the dimensions of the housing, the setting range for tripping point or value can be enlarged at will by imparting to the oblique or inclined surface a suitable position and of course different inclinations can be used. The width of the device can, under these circumstances, be limited to the dimensions determined by the components other than the bimetallic components.

In a preferred embodiment of the invention, the compensation bimetallic element is mounted pivotally and is rotatable angularly to various angular positions, set manually at will, so that it cooperates with the inclined surface at different points thereof, thereby providing a very large range of possible settings determined by the angular position and the inclined surface, the inclination of the surface, as well as the range of movement, in its own operating plane, permitted to the bimetallic element.

It is of particular advantage if the compensation bimetallic element is provided with a point contact for making contact with the inclined surface. This enables the available pivoting range, and therefore the range of possible settings, to be fully exploited. Moreover, the resulting point contact with the inclined surface increases the accuracy of the apparatus.

The inclined surface may be provided on the trip operator which can be constructed as a projection on a rocker arm or operator which carries out the tripping function and jointly with the compensation bimetallic element provides a variable bearing point or variable pivot. This type of embodiment is particularly applicable for use with differentially heated temperature-responsive tripping devices which respond not only to overload or overcurrent but also to differential phase loads.

Another feature of the invention which reduces the dimensions of the apparatus is the provision of a compensation bimetallic element displaceable in the working plane of the trip element by means of a threaded adjustment element fixed to engage the bimetallic compensation element and variably provides a pivot point for it in the working plane of the trip element. The threaded adjustment element, which may be a screw, makes it possible to set the trip point without having to enlarge the tripping device beyond dimensions determined by its other components. The adjustment made in the plane of the working trip, constituting the plane of deflection of the compensation bimetallic element, can be superimposed over the angular displacement adjustment of the compensation bimetallic element, relative to the inclined surface, in a plane perpendicular to the working plane of the trip element.

In a preferred embodiment of the invention, the compensation bimetallic element is U-shaped. The gap between the legs of the U is adjustable by means of an adjustment screw, as before described, to vary positions of its effective pivot in its working plane. The adjustment screw will provide a pivot point for deflection of the compensation strip. In this way the effective length of the compensation bimetallic strip or element is much reduced while its actual length is maintained. This reduction of the effective length of the compensation bimetallic strip allows increased angular displacement.

An additional feature or advantage of a tripping device in which at least one working bimetallic element or strip extends parallel with a wall of the housing is that the trip or trip switch can be arranged between the working or actuating bimetallic strip and the wall of the housing in line with the U-shaped compensation bimetallic element or strip. In this way the length of the tripping device can be reduced.

Other features and advantages of the tripping device in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawings in which:

FIG. 1 is a diagrammatic elevation section view of a first embodiment of a differential temperature-responsive tripping device in accordance with the invention;

FIG. 2 is a plan view of a slide in the device of FIG. 1;

FIG. 3 is a fragmentary plan view of a compensation bimetallic element in the device in FIG. 1; and

FIG. 4 is a diagrammatic fragmenary elevation view of another embodiment of a simple overcurrent tripping device in accordance with the invention.

While the tripping device in accordance with the invention will be described as applied to tripping an electrical circuit in dependence upon variations, from a given reference condition, in the operating conditions therein it will be understood that the principles of the present invention can be applied to tripping devices or controllers in automatic control in which a tripping function is to be carried out in accordance with variations of a phenomenon or operating condition represented by temperature variations which are proportionate to and representative of the variations of the condition in accordance with which the tripping function will take place.

As shown in FIGS. 1-3 inclusive a tripping device 1 has a housing as shown and comprises a plurality of sensing or working bimetallic strips or elements 2, 3 and 4. These working bimetallic elements are disposed side by side and are each fixed at one end, in this instance a lower end. The bimetallic elements are able to flex or deflect, in the plane of the drawing, from the position illustrated toward the right. The sensing bimetallic elements are responsive to temperature variations of electrical coil means, not shown, whose temperature conditions are represent-ative of and proportionate to operating conditions in the electrical circuit or the particular phases of a threephase main network, not shown, connected to terminals 5, 6, 7. For example, the coil means reflect overload conditions or unsymmetrical or differential phase loads.

A slide 8 is actuated by the bimetallic elements and a slide 9 likewise is actuated thereby. A trip element consisting of a rocker arm 10 is held at a point 11 on a slide 9 and is capable of being pivoted at a point 12 by the slide 8 until it depresses a plunger or trip element 13 of a trip or trip switch 14.

The tripping function or operation takes place in the usual manner either in the case of a strongly nonsymmetrical load, i.e. if only one of the working bimetallic strips displaces the slide 8 longitudinally and the other working bimetallic strips retain the slide 9, or in case of a symmetrically actuating overcurrent or overload, i.e. if all three working bimetallic elements displace the slide 8 and the slide 9 is held by a stop 15 of a compensation bimetallic strip or element 16 which compensates for temperature variations not representative of variations of an operating condition in the circuit, for example ambient temperature.

The compensation bimetallic element 16 is U-shaped and is anchored by its shorter leg 17 to a bushing 18 supported rotatably in a wall 19 of the device housing. The rotatable bushing is provided externally of the housing with a pointer 20 serving as a handle for rotatably moving the bimetallic strip 16 to angular positions indicated by the pointer 20 on a scale 21.

The bushing 18 is internally threaded and within this thread is disposed a threaded adjustment element or screw 22 having a point which engages the free leg of the U- shaped compensation strip 16 and provides a hearing or pivot therefor. The stop 15, is therefore adjustable in the plane of the drawing by means of the adjustment screw .4 22 and perpendicular to a plane of the drawing by means of the pointer 20. Moreover, it will be noted that the bimetallic strip 16 due to its U-shape is so short that it can be arranged above the trip switch 14 so that I10 additional room is required inside the device housing.

The slide 9 is provided with an inclined surface 23 in the region of contact with the compensation bimetallic strip 16. This surface is inclined relative to the pivoting or working plane of the compensation bimetal strip and also relative to the pivoting or working plane of the trip element 10. This working plane is the plane of the drawing. The compensation bimetallic strip 16 is pointed as illustrated in FIG. 3 so that it engages the inclined surface 23 with a small or point contact.

If the pointer 20 is displaced angularly through an angle for setting the tripping point of the apparatus the slide 9 will have to travel a distance between its nonoperative position and the point where it meets the bimetallic element 16 different from that it has to traverse before such angular displacement. Thus an overcurrent, for example, which causes tripping of the switch can be made to vary. The adjustment of the screw 22 can be, for example, factory set. It can thus be seen that in effect a variable pivot point for the operator 10 is established by the inclined surface and the stop 15 on the compensation strip 16.

A single-phase overcurrent trip device is shown in FIG. 4. In this instance a single working bimetallic element 24 acts on or displaces longitudinally a slide 25 when heated in the usual manner by a coil heated by current and reflecting changes in this current caused by changed operating conditions. The slide 25 has a free end 26 functioning as a stop for a trip element constructed as a rocker arm 27 pivotally mounted. This rocker arm bears with a projection 28 thereon on a compensation bimetallic strip 29 which has a free end engaging the projection. A free end 30 of the rocker arm or operator 27 acts on a trip element 31 of a trip or trip switch 32 to carry out tripping, for example a disconnect function or the like.

In this instance an inclined surface 33 is provided on the projection 28 of the rocker arm 27. The compensation bimetallic strip 29 is rotatably supported in a wall 35 of the housing, of the tripping device shown fragmentarily, by means of a pivot 34. A pointer-like handle 36 is mounted on the pivot externally of the housing by means of two nuts 37 for rotating the bimetallic strip 29 in a plane normal to the plane of the drawing. This will displace the inclined surface in this plane in the same Way as heretofore described. Moreover an adjustment screw 38 is provided in the wall of the housing which provides an adjustment in the pivot for the bimetallic strip somewhat like the adjustment screw in the first described embodiment.

The angular movement of the bimetallic element in conjunction with the inclined surface 33 allows setting of the trip point at which tripping is effected by overcurrent, for example. The adjustment screw 38 allows adjustment of an associated scale in the factory.

Those skilled in the art will understand that instead of a trip operator in the shape of a rocker arm 10 a barlike trip operator, not shown, may be used which extends substantially perpendicular to the two slides 8, 9, is loaded longitudinally by a spring, engages a slide and is disengaged therefrom by means of the other slide.

While preferred embodiments of the invention have been shown and described it will be understood that many modifications and changes can be made within the true spirit and scope of the invention.

What I claim and desire to be secured by Letters Patent is:

1. Temperature-responsive tripping device comprising, a trip, means tripping said trip comprising temperatureresponsive means responsive to temperature variations, a first bimetallic element responsive to said temperature variations, a compensation second bimetallic element defiectable in a given plane for responding to and compensating said device for other temperature variations, operator means comprising a pivotally mounted rocker arm cooperative with said second bimetallic element operable by said first bimetallic element for tripping said trip and the movement of which is compensated by said second bimetallic element so that said trip is operated by said operator means in a compensated condition, means for variably setting selectively a range of responses of said device to the first-mentioned temperature variations comprising a projection on said rocker arm defining a surface inclined relative to said plane and along which said operator means and said second bimetallic element contact, and means for relatively moving said surface and said second bimetallic element in a second plane transverse to the first-mentioned plane thereby causing said second bimetallic element and surface to contact along different points on said surface.

2. Temperature-responsive tripping device comprising, a trip, means tripping said trip comprising temperatureresponsive means responsive to temperature variations, a first bimetallic element responsive to said temperature variations, a compensation second bimetallic element deflectable in a given plane for responding to and compensating said device for other temperature variations, operator means cooperative with said second bimetallic element operable by said first bimetallic element for tripping said trip and the movement of which is compensated by said second bimetallic element so that said trip is operated by said operator means in a compensated condition, means for variably setting selectively a range of responses of said device to the first-mentioned temperature variations comprising means defining a variable pivot for said operator means comprising a surface inclined relative to said plane and along which said operator means and said second bimetallic element contact, said second bimetallic element defining jointly with said inclined surface the position of said variable pivot at different positions in the first-mentioned plane, and means for relatively moving said surface and said second bimetallic element in a second plane transverse to the firstmentioned plane thereby causing said second bimetallic element and surface to contact along different points on said surface.

3. Temperature-responsive tripping device comprising, a trip, means tripping said trip comprising temperatureresponsive means responsive to temperature variations, a first bimetallic element responsive to said temperature variations, a compensation second bimetallic element deflectable in a given plane for responding to and compensating said device for other temperature variations, operator means cooperative with said second bimetallic element operable by said first bimetallic element for tripping said trip and the movement of which is compensated by said second bimetallic element so that said trip is operated by said operator means in a condition compensated for said other temperature variations, means for variably setting selectively a range of responses of said device to the first-mentioned temperature variations comprising means defining a surface inclined relative to said plane and along which said operator means and said second bimetallic element contact, means for relatively moving said surface and said second bimetallic element in a second plane transverse to the first-mentioned plane thereby causing said second bimetallic element and surface to contact along different points on said surface, said means defining said inclined surface comprising a bar movable axially in said firstmentioned plane having said inclined surface disposed inclined relative to said plane transversely thereof, means joining said bar to said first bimetallic element for axial movement thereby, said operator means comprising a pivotally mounted rocker arm, and said inclined surface and said second bimetallic element jointly fixing the pivot of said rocker arm variably in both the first-mentioned and second planes.

References Cited UNITED STATES PATENTS 3,349,204 10/1967 Fair 33747 2,961,517 11/1960 Jelley 337-45 2,878,344 3/1959 Gustafson et a1. 337-338 OTHER REFERENCES German applications: 1,075,708 (February 1960), H. Kummer. 1,128,012 (April 1962), A. Dorries.

BERNARD A. GILHEANY, Primary Examiner DEWITT M. MORGAN, Assistant Examiner U.S. Cl. X.R. 

